The present invention relates to a device for measuring and displaying the operating autonomy of a storage battery.
As is known, cordless portable devices, such as cellular phones, videocameras, power tools and the like, are conventionally power supplied by portable storage batteries.
A problem frequently encountered in the use of the above mentioned devices is that the user must frequently know, within a set tolerance range, the operating autonomy of the device before recharging its storage battery.
A first group of prior devices of the above mentioned type which can provide the above mentioned autonomy information to a user, comprises devices adapted to normally display said information on a displaying scale including a plurality of displaying bars, for example from 3 to 7 bars.
However, in some cases, such a displaying method depends on the skillness of the user, who must associate a time, as measured in hours or minutes, with the displayed bar number.
Depending on the used device, the storage battery autonomy is conventionally determined either by using the battery discharging curve, i.e. by measuring the discharging voltage thereof, or by using counting devices designed for changing their counting rate depending on the electric current circulating therethrough.
In this connection it should be pointed out that, frequently, the adopted displaying scale is of a non-linear type.
Thus a main problem, affecting the mentioned prior art devices, is that prior approaches are sufficiently accurate only in those cases in which the battery supplies a nearly constant current therefore they cannot be used on a cellular phone drawing a quickly changing current.
Further autonomy displaying methods are based on chemical devices, designed for displaying wordings, for example the word "GOOD" at two displaying points on the same device, for example an electric accumulator, the word "GOOD" being displayed as confused letters as the storage accumulator discharges.
A prior display system which has been designed for actually displaying an autonomy time by minutes, has been designed and applied to videocamera Li-ion batteries.
This system, however, has the drawback that the user apparatus must be preset for easily reading this information stored in the battery, and that is the system itself (i.e. the videocamera) which operates to display the remaining or autonomy time in minutes, on a display associated therewith.
Thus the storage battery and device power supplied thereby would constitute an integral article which could not be separated into the two component parts thereof.
Thus, a requirement exists of accurately detecting the autonomy of a storage battery used in a lot of different battery supplied devices.